ASA 127th Meeting M.I.T. 1994 June 6-10

2pAO10. Characteristics and seasons of blue and finback whale sounds along
the U.S. west coast as recorded at SOSUS stations.

William C. Cummings

Oceanogr. Consultants, 5948 Eton Ct., San Diego, CA 92122

Paul O. Thompson

San Diego, CA 92103

Blue whale sounds were doublets, each member lasting about 19 s. ``A''
sounds mostly occurred at 19.7 Hz; ``B'' at 22.2 with a short tail at 19.8. A
few individual whales appeared to call for hours or perhaps days within
hydrophone range with a constant background din of like signals. Sounds
occurred in June--December, peaking as a high-level chorus in
September--October and increasing ambient noise up to 20 dB. Interseasonal
occurrence patterns at the same stations were remarkably similar. There was no
clear evidence of longitudinal migration in the broad area, Mexico--Canada.
These sounds, compared with subsequent blue whale recordings elsewhere,
strongly suggest a dialect. Finback sounds mostly were doublets, each lasting
about 1 s. The first member shifted downward (25.5--15.6 Hz) as did the second
(34.6--17.5 Hz). Intervals between signals of a series varied from 9--21 s.
Finback sounds were rare in summer, but numerous in the form of winter and
spring choruses after nearly all blue whale sounds ceased. Localizations showed
that the finbacks swam about 6 kn, and they had a source level of 183 dB re: 1
(mu)Pa, 1 m. Assuming even rough correlation between numbers of whales and
sounds, SOSUS was able to reveal the seasonal occurrence and abundance of blue
and finback whales over the entire western U.S. coastal region.